Liquid fuel pumping apparatus



Dec. 23, 1969 K. A. w. KEMP ET A LIQUID FUEL PUMPING APPARATUS FiledMarch 13, 1968 Q mm KEN ETH 87M 1- 3,485,175 LIQUID FUEL PUMPINGAPPARATUS Kenneth Albert Walters Kemp and Terence Redvers Wheeler,London, England, assignors to 'C.A.V. Limited, Acton, London, EnglandFiled Mar. 13, 1968, Ser. No. 712,771 Claims priority, application GreatBritain, Mar. 28, 1967, 14,060/67 lint. Cl. F04b 23/04, 19/02, 3/02 US.Cl. 103-5 2 Claims ABSTRACT OF THE DISCLOSURE A liquid fuel pumpingapparatus for supplying fuel to a combustion engine, and comprising apumping piston reciprocably accommodated within a bore, means for movingthe piston in one direction to reduce the volume of the pumping chamber,a passage extending from the pumping chamber, a one way delivery valvemounted in said passage, and a spill path extending from the passage ata point intermediate the pumping chamber and the delivery valve, saidspill path being arranged to be opened at a predetermined point duringthe movement of the piston in said one direction to release the pressurein the pumping chamber, thereby to permit said valve to close, and theeffective area of said spill path diminishing during continued movementof the piston in said one direction.

This invention relates to liquid fuel pumping apparatus for supplyingfuel to internal combustion engines and of the kind comprising a pumpingpiston reciprocably accommodated within a bore, means for moving thepiston in a direction to reduce the volume of the pumping chamberdefined by the piston and the bore, a passage extending from saidchamber and through which fuel flows in a direction from said chamber tothe engine and a one way delivery valve mounted in said passage, saidvalve being opened by the pressure of fuel created in said chamber whenthe piston is moved in said one direction the valve when closing servingto displace fuel in the direction opposite to said one direction.

The object of the invention is to provide such an apparatus in a simpleand convenient form.

According to the invention in an apparatus of the kind specified a spillpath extends from said passage at a point intermediate the pumpingchamber and the delivery valve, said spill path being arranged to beopened at a predetermined point during the movement of the piston insaid one direction thereby to relieve the pressure in the pumpingchamber to permit said valve to close, the effective area of said spillpath diminishing during continued movement of the piston in said onedirection thereby to restrict the rate of flow therethrough.

One example of a liquid fuel pumping apparatus in accordance with theinvention will now be described with reference to the accompanyingdrawing which is a part sectional side elevation of part of an apparatusin accordance with the invention.

Referring to the drawing there is provided a body part 10 in which ismounted a rotary cylindrical distributor member 11. The distributormember is coupled to an input shaft not shown and is arranged to bedriven in timed relationship with the engine to which fuel is to besupplied. At one end of the distributor member is formed a transversebore 12 in which is mounted a pair of reciprocable plungers 50.Moreover, surrounding the distributor member at this point is an annularcam 51 and having a plurality of diametrically disposed inwardlyextending cam lobes. As the distributor member rotates the cam lobes acton rollers 52 respectively the rollers nited States Patent 0 impartinginward movement to the plungers. The plungers 50 together with the camand rollers define a pressure pump.

The transverse bore 12 is in communication with one end of a bore 13which extends longitudinally Within the distributor member. The oppositeend of the bore is closed by means of a plug 14 and this end of thedistributor member is coupled to the rotary part of a fuel feed pump 15.The outlet of the feed pump is in communication with a passage 16 formedWithin the body part and the inlet of the feed pump communicates with asource of fuel.

The passage 16 is in communication with an annular feed gallery 17 whichis formed on the body part and from which at one point, extends acylindrical chamber 18. This chamber accommodates an angularly movablethrottle member 53 which is arranged to proportion the flow of fuelthrough a pair of passages 19, 20. The passage 19 communicates with anannular passage and passages 19a and these together with the passage 20extend to the cylindrical bore in the body part in which the distributormember 11 is mounted. Moreover, for registration with the passages 19a,passage 21 is provided and for registration with the passage 20 apassage 22. is formed in the distributor member. The passages 21 and 22communicate with the opposite ends of the bore 13. The communicationbetween the passages 19a, 20 and 21, 22 is arranged to take place duringthe filling stroke of the apparatus.

Mounted within the bore 13 is a reciprocable pumping piston 23 having anannular groove 24 defined in its periphery intermediate its ends.Moreover, the end portions of the pumping piston are of reduceddiameter. The space defined by the pumping piston, the bore 13 and theplug 14 constitutes a pumping chamber 25 and from this chamber extends adelivery passage 26. The delivery passage is arranged to register inturn as the distributor rotates, with a plurality of outlet ports 27formed in the body part and in communication respectively with nozzles54 mounted so as to direct fuel into the combustion chambersrespectively of the associated engine.

Also formed in the distributor member is a spill path which isconstituted by a radial passage 27a which is in communication with theoutlet passage 26 by means of a longitudinal groove 28 formed on theperiphery of the distributor member, the groove 24 formed in the pumpingpiston 23 and a further radial passage 29 extending from the bore 13 ata point axially removed from the passage 2.7a. The further radialpassage 29 during an injection stroke of the apparatus communicates witha spill port 30 defined in the body part. Furthermore, another radialspill passage 31 is formed in the distributor member and extends fromthe bore 13 at a point axially removed from the passage 29. The passage31 is arranged to register during an injection stroke of the apparatus,with a spill port 32 formed in the body part and which is provided witha pressurizing valve 55.

The relative positions of the various passages in the distributor memberwill become apparent from the description of the mode of operation ofthe apparatus.

During a filling stroke of the apparatus when the plungers 50 arepermitted to move outwardly by the cam lobes .fuel is fed by way of thepassages 21 and 22 to the bore 13. The relative quantities of fuelflowing through these passages determines the amount by which thepumping piston moves towards the transverse bore 12. The quantity offuel which enters by Way of the passage 22 determines the quantity offuel which will be supplied during the next injection stroke of theapparatus. It should be pointed out that during the filling stroke thepassages 26, 27a, 29 and 31 are closed. At the end of the filling strokethe pumping piston 23 will have assumed a position to the left of thatin which it is shown in the' drawing and the bores 12, and 13 will becompletely filled with fuel.

As the distributor rotates the delivery passage 26 will be brought intoregister with an outlet port 27 and the passages 21 and 22 will be movedout of register with the passages 19:: and 20 respectively. Duringcontinued rotation of the distributor member inward movement will beimparted to the plungers 50 and fuel under pressure will act on the lefthand end of the pumping piston 23- and cause it to be moved towards theplug 14. During this movement fuel is expelled from the pumping chamber25 and flows by Way of the delivery passage 26 to the outlet port. Itshould be mentioned that each outlet port is provided with a deliveryvalve 56 which is spring loaded and which opens to permit the flow offuel to the injection nozzles. Moreover, when the pressure in thepumping chamber is relieved as will be described, the delivery valve 56closes and in so doing a predetermined small quantity of fuel is urgedin the reverse direction to that in which it flows during the deliveryof fuel to the engine to provide rapid relief of pressure at theinjection nozzle to terminate delivery abruptly but to retain acontrolled residual pressure in the delivery pipe.

At a predetermined position in its movement towards the plug 14 thegroove 24 on the pumping piston 23 is exposed to the radial passage 27a.Moreover, the groove 24 is exposed to the further radial passage 29 andthis is in communication with the spill passage 30. The result of thisis that the pressure of fuel within the pumping chamber is relieved andthe delivery valve 56 closes. The fuel which is forced back by thedelivery valve flows through the spill path previously defined and inaddition to this quantity of fuel the surplus fuel from the pumpingchamber 25 also flows throgh the spill path.

The pumping piston continues its movement towards the plug 14 and duringthis movement the effective area of the spill path is reduced so thatthe rate at which fuel can flow through the spill path is reduced. Thereduction in the area of the spill path is brought about by the factthat the groove 24 is moving out of register with the further radialpassage 29. At the same time the end of the pumping piston is coveringthe delivery passage 26 and as soon as this passage is completelycovered by the pumping piston an hydraulic lock is created in thepumping chamber 25. The hydraulic lock prevents further movement of thepumping piston and this is brought to a halt in a predeterminedposition. As soon as the pumping piston is halted surplus fuel containedWithin the bore 12 and the end of the bore 13 in communicationtherewith, flows through the passages 31 and 32, past the pressurisingvalve 55 which is located in this passage.

The restriction of the spill passage as described minimises the risk ofcavities forming in the respective outlet ports 27 when the deliveryvalves 56 therein contact their seats. The closing of the deliverypassage 26 to create an hydraulic lock in the pumping chamber likewiseprevents cavitation in this chamber.

At the end of the injection stroke the pumping piston is therefore in apredetermined position and there are no cavities in the pumping chamber,so that the quantity of fuel which flows through the passage 22 duringthe next filling stroke is exactly the quantity of fuel which will besupplied to the engine during the next delivery stroke neglecting theleakage which takes place.

Having thus described our invention What we claim as new and desire tosecure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying fuel to an internalcombustion engine and comprising a member in which is defined a bore, apumping piston reciprocably accommodated within the bore, a pressurepump for supplying liquid under pressure to one end of said bore therebyto move the pumping piston in one direction towards the other end of thebore, the pumping piston and the other end of the bore defining apumping chamber, the volume of which is reduced during movement of thepumping piston in said one direction, a delivery passage extending fromsaid pumping chamber and through which fuel flows from the pumpingchamber to the associated engine during movement of the pumping pistonin said one direction, a one Way delivery valve mounted in said passage,said valve being opened by the pressure of fuel created in said chamberwhen the piston is moved in said one direction, the valve closing whensaid pressure is relieved and acting to allow a small quantity of fuelto flow towards the pumping chamber, a spill path extending from saidpassage at a point intermediate the pumping chamber and the deliveryvalve the spill path being arranged to be opened at a predeterminedpoint during the movement of the piston in said one direction thereby torelieve the pressure in the pumping chamber to permit said valve toclose, the effective area of said spill path diminishing duringcontinued movement of the piston in said one direction thereby toprovide increasing restriction to the flow of fuel therethrough.

2. A liquid fuel pumping apparatus as claimed in claim 1 in which saiddelivery passage extends laterally from said bore at a position to becovered by said piston at the end of the movement thereof in said onedirection, and in which said spill path as defined by a pair of passageswhich break into said bore at axially spaced points and by a grooveformed in the periphery of the piston, one of said pair of passagescommunicating with the first mentioned passage and the other of saidpair of passages communicating with a drain, said groove serving toplace said pair of passages in communication with each other at saidpredetermined point during the movement in said one direction of thepiston, further movement of the piston serving to move the groove out ofregistration with one of said pair of passages thereby to restrict therate of flow of fuel through said spill path.

References Cited UNITED STATES PATENTS 2,178,902 11/1939 Clausen 103-412,384,011 9/1945 Bremser 103-41 3,115,838 12/1963 Koester 103-4l3,320,893 5/1967 Koster 10341 3,356,031 12/1967 Glikin 103-2 WILLIAM L.FREEH, Primary Examiner U.S. Cl. X.R. 1032,

